Propeller



Nov. 11 1924- I G. w. MORROW PROPELLER Filed Dec. 27, 1922 3' Sheets-Sheet 1 By M INVEN TOR. 62 0562 :44 Mme/e0 w.

ATTORN /YS.

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G. w. MORROW PROPELLER Filed Dec. 27 1922 I5 Sheets-Sheet 2 INVENTOR. J 650565 #14 MO/FEO w w v ATTORN YS.

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G. W. MORROW PROPELLER Filed Dec. 27, 1922 3 Sheets-Sheet 5 IM/FNTUR. GEORGE WMORRUW ATTORNEYS.

Patented Nov. ll, 1924.

barren stares earner GEORGE W. MORROW, OF SAN FRANCISCO, CALIFORNIA, ASSIGNOR TO CLOVERLE AF PROPELLER COMPANY, OF SAN FRANCISCO, CALIFORNIA, A CORPORATION OF CALIFORNIA.

PROPELLEB.

Application filed December 27, 1922. Serial No. 609,179.

' the following is a specification.

This invention relates to screw propellers for vessels of all classes.

The ob ect of the invention 1s to provide a more efiicient design for absorbing power and creating thrust, both in a forward and reverse direction than is possible with the standard designs now in use.

This object is accomplished b developing. the following edge of each bla e forwardly into an easy stream line surface and thereby forming a portion of said blade, which has the efl'ect of releasing the thrust gradually at the following edge and so reducing cavitation and increasing efficiency, particularly in the reverse direction. These blades have a slightly increasing pitch fromthe hub to the tip, being about 5% less at the hub than at the tip. The tip of the leading edge is curved rearwardly and the tip of the following edge is curved forwardly on a circle of radius approximating 5 inches for all ordinary wheels. The extreme diameter, pitch ratio and surface ratio and number of blades are to be determined in the usual way and to suit the requirements which may be exacted.

One form which my invention may assume is exemplified in the following description and illustrated in the accompanying drawings, in which Fig. 1 shows a rear elevation of a propeller embodying my invention.

Fig. 2 shows an edge view of the same.

\ Fig. 3 shows a longitudinal section through the hub and one of the blades.

Fig. 4 shows cross sections of the blade various radii.

' Fig. 5 shows a cross section of the blade on the lines 1 to 6, inclusive of Fig. 3.

Fig. 6 shows a cross-section of one of the blades, taken on the line 66 of Fig. 1.

Fig. 7 shows a perspective view of my propeller.

The propeller comprises a hub portion 10 and a plurality of fan-shaped blades 11 disposed helically about the hub. Each blade is composed of two sections12 and 13 of unequal widths. These sections are curved oppositely in a .fore and aft direction, the wider section having its tip curved rearwardly and being effective for forward propulsion, while the narrower one has its tip curved forwardly and is effective for driving astern.

Loss of power, due to cavitation, is caused by the formation of vortex spirals produced by the flow of water from the pressure to the suction side near the tip of'a propeller blade'. By forming each blade in two sections and curving them in the manner shown, the effect of these vortex spirals will be considerably reduced.

The pitch of the blades increases axially, being about 5% greater at the outer end than at the hub. The rearward incline or rake usually given to blades may be omitted and the formula for determining the thickness of the blades may be that of the lowest constant of the American Bureau of Shipping.

The advantagev of this design is that the blades concentrate and entrain the water, thereby producing a greater thrast for the same diameter of blade. Vibration is considerably reduced and a much larger amount of power is effectively absorbed in driving astern.

The forward driving action of the blade is produced in a large measure by the section 12 which may be considered as being de veloped along the lines of a standard screw blade. The presence of the section 13 at the rear thereof causes a gradual release of the thrust and the reduction of cavitation, owing to its stream line design. Its rear section will also be efiective when the propeller is driven in a reverse direction. Therefore, the present device becomes of considerable advantage in connection with tugs, ferry boats and the like where considerable driving astern is necessary. I The extreme diameter, pitch ratio, surface ratio and number of blades can be varied as desired and are determinable by any of the standard methods in use for helical screws.

The-sections of the blade near the tips are hollowed out on the driving faces as shown onfthe cross section 5*5 of Figure 5, thus affording an easy stream-line surface for the purpose of releasing the waters. The opposite faces of the blade sections near the tips gradually merge or fade together, thus reducing the curvature and increasing the efficiency, particularly in a reverse direction.

assets Having thus described my invention, what I claim and desire to secure by Letters Patent is:

l. A screw propeller, comprising a hub,

a plurality of fan-like blades disposed helically about the hub, each blade being bifurcated at its tip, with the bifurcated portions curved oppositely in a fore-and-aft direction adjacent their tips, the portion of the blade adjacent the leading edge being substantially in the form of a standard screw-blade and the portion of the blade adjacent the following edge being curved for- 7 wardly and merging gradually into the other portion of the bladewhereby to .form a stream-line surface for the release of water from contact with the blade. l

2. A screw propeller comprising a hub, a plurality of tan-like blades disposed helically about the hub, each blade being com neiaaee posed of two sections of unequal widths and curved in opposite directions.

3. A screw propeller comprising a hub, a plurality of fan-like blades disposed helical-i ly about the hub, each blade being composed 2 posed of two sections, the section toward the leading edge being wider than the other section and having its tip curved rearwardly for forward propulsion and the other wing having its tip curved forwardly for driving astern.

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